Selecting An Appropriate Bolt
 

https://www.mcmaster.com/#screws/=17gvyip

https://www.mcmaster.com/#standard-h...crews/=17gvynp

if the local hardware is sparse on 6mm bolts n nuts n washers then assemble a list of whatever you need on the shelf order that and a box each of quality 6mm bolts n nuts long enough to reach then cut down to other smaller sizes.

It is my experience grade 5 6mm bolts used as lower rack bolts need replacement every 5-6000 miles. That is if going far, replace these bolts.